Whole House fan switch

When I bought my house 6 years ago, it came with this thing I had never heard of, a whole house fan. It's been a rockstar in the spring and fall, when its warm enough outside that the house heats up, but not so hot as to really need the AC. A couple of years ago, the rotary switch control crapped out on me. I ended up taking the old one out to grainger, and over the course of a few weeks they came up with some options for replacing it. The original switch was apparently old as hell. The replacement, was a 3amp rotary switch, similar to this one: Broan Electronic Variable-Speed Fan Control in White-57W - The Home Depot. It worked...for the most part. Only the top 25% of the switch would actually allow enough juice through to power the fan. I could only run the fan for an hour or 2 before the switch started to feel physically too hot. At this point, the switch has given out entirely. As it is springtime, and we should have another several weeks before it gets too hot, and I have to turn on the AC, I am debating on whether I should replace the switch again, or start looking at other options. I did find a 5amp control here: 600-Watt Vari-Speed Motor Control-vari-speed - The Home Depot Having a higher maximum amperage, in my mind anyway means that it wouldn't burn up as fast as the current (no pun intended) switch did.

I have no idea on the age of the fan. Based on the yellowing of the plastic louvers that fell down several years ago, I would guess that its really old. Something new might not draw as much power. Thoughts?

Whole House fan switch